1. Field of the Invention
The present invention relates to a vacuum pumping system, a driving method thereof, an apparatus having the same, and a method of transferring a substrate using the same.
2. Discussion of the Related Art
In general, a semiconductor device or a liquid crystal display (LCD) device is fabricated by repeating a deposition step of a thin film on a substrate, a photolithographic step using a photoresist, a selective etch step of the thin film and a cleaning step of the substrate several times or several ten times. These steps for a fabrication process of a semiconductor device or an LCD device may be performed using an apparatus having a process chamber under optimum condition.
Recently, a cluster including process chambers for treating substrates, a load-lock chamber for storing the substrates temporarily and a transfer chamber for moving the substrates into and out of the process chambers between the process chambers and the load-lock chamber has been widely used as an apparatus for fabricating a semiconductor device and an LCD device because of its superior treatment capability of large number of substrates in a short time period.
FIG. 1 is a schematic view showing a cluster according to the related art. The cluster may be used for manufacturing an LCD device as well as a semiconductor device.
In FIG. 1, a cluster includes a transfer chamber 70, a plurality of process chambers 80, first and second load-lock chambers 40 and 50, a transfer unit 10 and first and second load ports 20 and 30. The plurality of process chambers 80 and the first and second load-lock chambers 40 and 50 are connected to respective sides of the transfer chamber 70. The transfer unit 10 is connected to sides of the first and second load-lock chambers 40 and 50, and the first and second load ports 20 and 30 are connected to a side of he transfer unit 10.
Generally, a deposition step of a thin film on a substrate, an etch step of the thin film and a cleaning step of the substrate are carried out in the process chambers 80 under a high vacuum condition. The transfer chamber 70 serves as a space for transferring the substrate between one process chamber and another process chamber 80 or between one of the process chambers 80 and one of the load-lock chambers 40 and 50 using a transfer chamber robot 72. The transfer chamber 70 also keeps a vacuum condition. Slot valves (not shown) are set up between each process chamber 80 and the transfer chamber 70.
The transfer unit 10 may be referred to as an equipment front end module (EFEM). The transfer unit 10 serves as a space for moving an untreated substrate into the load-lock chambers 40 and 50 or for moving a treated substrate out of the load-lock chambers 40 and 50 into the outside using a robot 12 therein. The transfer unit 10 always keeps an atmospheric condition and is connected to the first and second load ports 20 and 30 with doors (not shown) disposed therebetween. Cassettes taking in substrates are disposed in the load ports 20 and 30.
An aligner 60 for flat zone alignment of a substrate disposed on the robot 12 may be equipped at a side of the transfer unit 10.
The first and second load-lock chambers 40 and 50 are disposed as a buffer between the transfer chamber 70 and the transfer unit 10 because the transfer chamber 70 is under a vacuum condition and the transfer unit 10 is under an atmospheric condition. The first and second load-lock chamber 40 and 50 are alternately under a vacuum condition and an atmospheric condition when the substrate goes in and out.
Slot valves are set up between the first and second load-lock chambers 40 and 50 and the transfer unit 10 and between the first and second load-lock chambers 40 and 50 and the transfer chamber 70.
Cassettes taking in substrates are disposed in the first load port 20 and the second load port 30, and the robot 12 transfers a substrate from one of the first load port 20 and the second load port 30 into the transfer unit 10. Next, after the robot 12 achieves flat zone alignment of the substrate in the align 60, the robot 12 transfers the substrate into one of the first and second load-lock chambers 40 and 50.
For example, if a door (not shown) of the first load-lock chamber 40 is open, the robot 12 loads the substrate in the first load-lock chamber 40. Then, when the robot 12 turns back, the door is closed, and a pumping step is performed to convert the first load-lock chamber 40 from the atmospheric condition into the same vacuum condition as the transfer chamber 70.
When the first load-lock chamber 40 is under the vacuum condition, a door (not shown) between the first load-lock chamber 40 and the transfer chamber 70 is open, and the transfer chamber robot 72 goes into the first load-lock chamber 40 to move the substrate into one of the process chambers 80.
After the substrate is treated in the process chamber 80, the substrate is taken out in reverse order of the above-mentioned processes. At this time, the substrate is transferred out of the transfer chamber 70 into the load-lock chamber 40 or 50, and then a step for venting the load-lock chamber 40 or 50 is performed to change the load-lock chamber 40 or 50 from the vacuum condition to the atmospheric condition. After the venting step, the robot 12 of the transfer unit 10 takes out the substrate in the load-lock chamber 40 or 50 and transfers the substrate into the cassette in the load port 20 or 30.
By the way, the cluster according to the related art requires a transfer chamber 70 under a vacuum condition and at least one load-lock chamber 40 or 50 so as to connect the process chambers 80 under a high vacuum condition and the outside under an atmospheric condition. This causes a large footprint of the cluster and high costs of the cluster due to the transfer chamber 70 and the transfer chamber robot 12.
Meanwhile, as stated above, because the load-lock chamber 40 or 50 is alternately under a vacuum condition and an atmospheric condition and the process chambers 80 and the transfer chamber 70 are always under a vacuum condition, the cluster should include a vacuum pumping system and a venting system.
FIG. 2 is a schematic view of a process chamber, a vacuum pumping system and a venting system according to the related art. As shown in the figure, a susceptor 87 is disposed within the process chamber 80 to load a substrate thereon, and a gas injection unit 84 such as a showerhead is disposed over the susceptor 87. The gas injection unit 84 is connected to a process gas storing unit 86 via a gas line 85 passing through a chamber lid 81 of a dome shape. An injector, which passes through a sidewall or a lower side of the process chamber 80 and protrudes within the process chamber 80, may be used as the gas injection unit 84. The chamber lid 81 may have various shapes without limitation on the dome shape.
A turbo molecular pump (TMP) 90 is disposed under the process chamber 80, and a pendulum valve 83 is disposed between the process chamber 80 and the TMP 90.
The vacuum pumping system includes a first exhaust line 91, a booster pump 98, a dry pump 99, and a second exhaust line 92. One end of the first exhaust line 91 is connected to a low part of the process chamber 80, and the booster pump 98 and the dry pump 99 are connected to the other end of the first exhaust line 91. One end of the second exhaust line 92 is connected to the TMP 90, and the other end of the second exhaust line 92 is connected to the first exhaust line 91 ahead of the booster pump 98.
The dry pump 99 may be referred to as a roughing pump and may be widely used under pressure conditions from atmospheric pressure to about 1 mTorr (millitorr). The dry pump 99 is classified into a CAM type and a screw type.
As schematically illustrated in FIG. 3, the booster pump 98 includes a cylinder 98a and two rotors 98b of a cocoon shape in the cylinder 98a, wherein the rotors 98b are uniformly rotated in opposite directions by driving gears at axes thereof, respectively.
Therefore, gases coming into an intake of the booster pump 98 are exhausted toward an outlet due to rotation of the rotors 98b, tightly closed in a space between the cylinder 98a and the rotors 98b, and the gases are gone out into the air through an additional pump, for example, the dry pump 99 of FIG. 2, behind of the booster pump 98.
Since a narrow gap of about 0.1 mm to about 0.3 mm is kept between the rotors and between the rotor and the cylinder, lubricating oil is not necessary. Thus, there is an advantage of vacuum exhaustion without oil.
A slow pumping line 93 extends from a fast pumping line 91, that is, the first exhaust line 91. Because the slow pumping line 93 has a smaller cross-sectional area than the first exhaust line 91, the slow pumping line 93 has a relatively low exhaust conductance and a relatively slow pumping speed as compared with the first exhaust line 91. If the pumping speed is fast at an early stage of pumping, the substrate and components of the apparatus may be damaged. Accordingly, the slow pumping line 93 is used to reduce the damages.
A three-way valve 96 is equipped between the process chamber 80 and the booster pump 98 so that the slow pumping line 93 diverges from the first exhaust line 91. One end of the slow pumping line 93 is connected to one outlet of the three-way valve 96, and the other end of the slow pumping line 93 is connected to the first exhaust line 91 between the booster pump 98 and the three-way valve 96. Therefore, an exhaust path of the gases is determined out of the slow pumping line 93 and the first exhaust line 91 by the three-way valve.
A middle valve 97 is disposed in the middle of the second exhaust line 92, and the middle valve 97 opens and shuts depending on working of the TMP 90.
To change the chamber under from the atmospheric condition to a vacuum condition using the above vacuum pumping system, the boost pump 98 and the dry pump 99, first, are driven, and gases are exhausted through the slow pumping line 93 by controlling the three-way valve 96. When the process chamber 80 is under a certain pressure, the three-way valve 96 is controlled again, and thus gases are exhausted through the first exhaust line 95 not the slow pumping line 93. At this time, the booster pump 98 and the dry pump 99 simultaneously work.
When the process chamber 80 is under a high vacuum condition, the pendulum valve 83 under the process chamber 80 is opened, and the process chamber 80 is pumped using the TMP 90 until the inside of the process chamber 80 is under an ultra high vacuum condition. Gases exhausted through the TMP 90 are exhausted through the booster pump 98 and the dry pump 99 via the middle valve 97 and the first exhaust line 93.
However, because the vacuum pumping system has a slow pumping speed, it is difficult to frequently use the vacuum pumping system, and the vacuum pumping system is widely used in a step for setting an apparatus.
Meanwhile, a venting system is commonly equipped for the load-lock chambers 40 and 50, which are alternately under the atmospheric condition and under the vacuum condition, and the venting system may be equipped for the process chamber 80 or the transfer chamber 70. That is, when the pressure in the process chamber 80 or the transfer chamber 70 become considerably low due to excessive vacuum pumping, the pressure in the process chamber 80 or the transfer chamber 70 should be adjusted by an optimum pressure by providing gases such as argon (Ar) or nitrogen (N2). Additionally, the chambers may be under the atmospheric condition in the case of immobilizing the apparatus for repair or in other needed case.
FIG. 2 shows the venting system of the process chamber 80. The venting system includes a venting line 88 and a needle valve 89. One end of the venting line 88 passes through the sidewall of the process chamber 80, and the other end of the venting line 88 is connected to a venting gas storing unit (not shown), which includes Ar or N2 gases therein. The needle valve 89 is set up in the middle of the venting line 88 and controls flow rate of the gases.
However, the related art venting system commonly adjusts the pressure of the chambers under the vacuum condition within narrow ranges. Thus, if the range of the adjusted pressure is widened, venting time should become longer.
If gases flow into the chamber in quantity to reduce the venting time, it is impossible to uniformly maintain the inner temperature of the chamber, and thus reproductivity of the processes is reduced. In addition, since degradation of the apparatus and generation of particles may be caused due to thermal impacts, there is limitation on periodically venting the process chamber during the processes.